1. Field of the Invention
The present invention relates to a non-reversible circuit device such as a circulator and an isolator for use as a high frequency device which operates in a microwave band.
2. Description of the Related Art
The configuration of a prior art non-reversible circuit device will be described with reference to FIG. 4. The device contains a disk-shaped ferrimagnetic plate 51.
A laminated substrate 52 is formed by laminating a plurality of insulation layers. A concavity 52a is formed in the center of the substrate 52.
First, second, and third central conductors 53, 54, and 55 comprising electroconductive plates of copper or the like are arranged at 120 degree intervals and have different heights in the vertical direction of the laminated substrate 52. The central conductors 53, 54, and 55 are electrically insulated from each other, and are arranged in such a manner that a part of the respective central conductors cross each other in the vertical direction of the laminated substrate.
One-side ends of the first, second, third central conductors 53, 54, and 55 are introduced to one surface (upper surface) 52b of the laminated substrate 52 via connecting conductors 56a, 56b, and 56c placed in through-holes (not shown) formed in the laminated substrate 52, and form input-output terminals 53a, 54a, and 55a, respectively.
Moreover, the other-side ends of the first, second, and third central conductors 53, 54, and 55 are introduced to the one surface (upper surface) 52b of the laminated substrate 52 via connecting conductors 57a, 57b, and 57c placed in through-holes (not shown) formed in the laminated substrate 52, and form input-output terminals 53b, 54b, and 55b respectively.
The ferrimagnetic member 51 is disposed in the concavity 51a of the laminated substrate 52. In this state, a DC magnetic field is applied to the ferrimagnetic member 51 by means of a magnet (not shown) disposed in the neighborhood of the part of the device where the first, second, and third central conductors 53, 54, and 55 cross each other. Thus, inputting and outputting is carried out through the input-output terminals 53b, 54b, and 55b. 
The ferrimagnetic member 51, the laminated substrate 52, and the magnet (not shown) are covered with a yoke (not shown in FIG. 4) to form a non-reversible circuit device. The non-reversible circuit device is mounted onto a circuit substrate. Moreover, capacitors mounted on the circuit substrate are connected to the input-output terminals 53a, 54a, and 55a of the first, second, and third central conductors 53, 54, and 55 via a wiring pattern.
In the case of the prior art non-reversible circuit device, the connecting conductors 57a, 57b, and 57c used to form the ground terminals 53b, 54b, and 55b are disposed at the positions in the device which are radially projected from the ferrimagnetic member 51. This causes a problem in that the size of the laminated substrate 52 is increased in the radial direction.
Moreover, since the capacitors are mounted on the laminated substrate 52, the space factor of the non-reversible circuit device is inferior, so that the size of the device is increased.
Accordingly, it is an object of the present invention to provide a compact non-reversible circuit device having a laminated substrate reduced in size.
According to the present invention, there is provided A non-reversible circuit device which comprises a ferrimagnetic member, and first, second, and third central conductors arranged on and/or in a laminated substrate at different heights in the vertical direction of the laminated substrate, wherein a part of the respective central conductors cross each other in the vertical direction of the laminated substrate, one ends of the respective first, second, and third central conductors constitute input-output terminals, and the other ends thereof are introduced to one surface of the laminated substrate to constitute ground terminals, and the ferrimagnetic member has electrode portions and is arranged on the one surface of the laminated substrate so that the ground terminals are connected to the electrode portions, respectively. Accordingly, the ground terminals of the central conductors can be positioned so as not to project from the ferrimagnetic member. Thus, the laminated substrate can be reduced in size. A small-sized non-reversible circuit device can be provided.
Preferably, the electrode portions are formed on one surface of the ferrimagnetic member opposed to the laminated substrate. Thus, the ground terminals can be easily connected to the electrode portions. The production efficiency is enhanced.
The ferrimagnetic member preferably has a side electrode portion formed on the side-surface of thereof so as to be connected to the electrode portions. Therefore, the electrode portions can be easily connected to the second yoke via the side electrode portion. Work for the connection can be easily performed.
Also, the ferrimagnetic member has a lower electrode portion formed on the other surface thereof so as to be connected to the side electrode portion. Therefore, the lower electrode potion can be securely connected to the second yoke, and the ground terminals can be securely grounded.
Preferably, the input-output terminals are formed on the one surface of the laminated substrate, respectively. Accordingly, the input-output terminals can be provided on the same surface of the laminated substrate. The wiring workability is enhanced.
Also, the input-output terminals preferably are formed so as to extend onto the side surface of the laminated substrate. Therefore, wiring can be carried out on the side surface of the laminated substrate, not projecting from the upper surface of the laminated substrate. A thin non-reversible circuit device can be provided.
Preferably, the device further comprises chip-type capacitors which are disposed on the one surface of the laminated substrate, and one-side electrodes of the capacitors are connected to the input-output terminals, respectively. Therefore, wiring for the capacitors can be easily performed. Thus, a small-sized, compact non-reversible circuit device can be provided.
Preferably, the non-reversible circuit device further comprises a first yoke accommodating a magnet and a second yoke accommodating the ferrimagnetic member and the capacitors, the first yoke being joined to the second yoke with the magnet being disposed above the central conductors whereby the first and second yokes form a magnetic closed circuit, the electrode portion formed on the ferrimagnetic member being connected to the second yoke to be grounded, the other-side electrodes of the capacitors being connected to the second yoke to be grounded. Accordingly, the capacitors can be compactly arranged. Thus, a small-sized, compact non-reversible circuit device, compared to a prior art one, can be provided.